Engine compartment ventilation

[ewengstrom]

Our boats come with a blower motor that seems rather useless. The original 3" vent hose(s) run down to below the aft cabin bunk and just end....even when the motor has been running you can start the blower motor and it's only sucking cool air.
Has anyone found a good way to route the pickup for the blower motor to somewhere near the top of the engine compartment?
My thoughts are that this will help reduce the temp in there and that cannot be a bad thing. We sail on the Potomac/Chesapeake and the temps here can reach the mid to upper 90's in the summer so any extra cooling cannot be a bad thing.
Anyone out there done something about this in the past???? I couldn't find anything on any earlier posts addressing this specific topic.

[Pete G]

This is on my list of things to tackle, so hoping you get responses.  In addition to the heat, there's a significant diesel smell in the cabin - after 37 years, the cushions, although in great shape, have a smell we're unable to remove.  We removed a couple of the cushion covers and tried Tide, Borax, Nature's Miracle - all with no luck.  And the smell of the foam - eek!

[scgunner]

Eric,

You're right the blower motor is useless, I think it's a hold over from the days of gasoline motors. It's purpose is to draw gas fumes out of the engine compartment to prevent explosion or fire not for cooling which is why you're supposed to run it before you start your motor. You might be searching for the answer to a problem that doesn't exist. The engine compartment is well ventilated and the only time I've ever had an overheating problem has been due to a blockage in the raw water system.

Pete,

You don't have a ventilation problem you've got a diesel leak problem.

[ewengstrom]

Kevin,
Well...that's a possibility regarding venting gas fumes....but I don't think I've ever heard of a C34 that was supplied with a gas motor, the first boats came with a M25 diesel, correct?
I just wonder why Catalina would have continued supplying these boats (for years) with a system that wasn't relevant. That's just an easily eliminated cost for the manufacturer.
My thoughts were to run the blower motor on hot days when it will run for hours on end and thereby help remove excess heat from the engine compartment. Perhaps the blower can't handle the heat....and if that's the case I'll eliminate it myself. 

[Kyle Ewing]

I run mine before starting out of habit from my time on gas powered runabouts, but also to remove any propane that may have settled (unlikely).  I also run the blower while motoring a long time as the aft cabin heats up after several hours.

[scgunner]

Eric,

You're right again, no C34 ever came with a gas motor by the mid '80s the days of the venerable old Atomic 4 were coming to an end. The blower motor however remained, possibly due to a building code regulation. Also some owners might feel more comfortable running the blower for 5 minutes before starting the motor. When I had my gas motor powered C27 the hot tip was to open a hatch and smell for fumes and that was recommended before running the blower. Nowadays with the C34 I just fire up the motor and don't give it a second thought.

[ewengstrom]

This is on my list of things to tackle, so hoping you get responses.  In addition to the heat, there's a significant diesel smell in the cabin - after 37 years, the cushions, although in great shape, have a smell we're unable to remove.  We removed a couple of the cushion covers and tried Tide, Borax, Nature's Miracle - all with no luck.  And the smell of the foam - eek!

Pete, when we bought Ohana she had been pretty neglected over the years, one of the problems we encountered was an oily/diesel smell that permeated everything below. My wife recovered all the interior cushions and thoroughly washed all the foam and there is no hint of the old pungent smell anymore. It took a while to dry the foam out but it was worth it IMHO. While I had the interior woodwork completely removed I also washed the bilge out, there had been a pretty big oil spill down there and the entire bilge was coated with a dry black film....a rather oily dry film. With the flooring removed this wasn't as nasty or tough a job as it might sound.

[KWKloeber]

Eric

Have you tried OdorBan on the diesel odor?

One "cool" mod is a water-cooled exhaust in place of the pipe riser.
Check on the TechWiki:   Engine > Cooling > article by Bill Shreeves

[High Current]

We don't have gasoline but many of us do have propane stoves; propane is heavier than air and can theoretically settle in the bilge, also creating an explosion hazard - if you're unlucky enough not to notice the smell as it diffuses anyway.  But it might explain why Catalina felt the blower was necessary.

[KWKloeber]

ABYC H-32 VENTILATION OF BOATS USING DIESEL FUEL

32.5.3
Combustion Air – Ventilating provisions and openings to the machinery space provided for
supplying combustion air shall accommodate at least the sum of the maximum air requirements
specified by the engine manufacturer(s) for each propulsion and auxiliary engine(s) in that
space

32.5.4
Additional Uses of Ventilation - Power or natural ventilation may be needed to control
compartment temperature. Power ventilation may also be used in the machinery space for odor
control and personnel comfort while servicing equipment.

[Pete G]

With the flooring removed this wasn't as nasty or tough a job as it might sound.
[/quote]

I've been pretty focused on getting the topside squared away, but slowly moving below decks.  Trying to weigh what I'll do while Maris Otter is on the water vs. waiting until she's on the hard.  Planning to remove all of the sole for a complete clean - good advice.  The water tank vent line to the stanchion wasn't connected, so the teak panelling is rotted.  Also need to install an automatic bilge pump.  And new wiring harness.  And new plumbing.  And... 

[rmjohns]

At least on my 1998 model, I don't think the blower would help much with a propane leak. Both the intake and exhaust for the blower are up around the propeller shaft. There's a lot of volume in the bilge below that.

I do think running it helps with the smell of a diesel engine running right there, though the hoses could probably be better located to help with that. My intake and exhaust for the blower are straight across from each other. I think putting exhaust hose higher in the engine compartment might help

Rob.

[ewengstrom]

Rob, you echo my thoughts exactly. Propane would end up deep in the bilge (well below the blower motor pickup) as well as behind the engine so this ventilation seems to be aimed more at the gasoline vapor ventilation that KW brings up.
I'm still going to examine the compartment to see if there is a good way to ventilate the area better......It doesn't appear this has been a concern in the past based on the lack of posts regarding this subject.
Maybe worth the effort...maybe not, we'll see.

[waughoo]

I replaced mine with a jabsco squirrel cage blower fan.  I replaced the 3" wire reinforced vinyl hose with new 3" nylon spiral "fabric" hose that extends all the way to the bulkhead behind the engine.  I run this anytime the engine is running to keep the machinery space cooler (alternator performance) and to keep the hot oil smell to a minimum in the aft cabin.  I can feel the exhaust air temp from the helm and it is carrying heat away from the compartment.  It has also reduced/eliminated the oily smell from the aft cabin.  This is further helped by putting a catch can on the crank case vent.

[Stu Jackson]

It has also reduced/eliminated the oily smell from the aft cabin.  This is further helped by putting a catch can on the crank case vent.

There's always this sure fix:

Breather Hose 101 (w/ K&N Filter Pictures from Rick Allen)

http://c34.org/bbs/index.php/topic,8875.msg63915.html#msg63915

and Noah's:  http://c34.org/bbs/index.php/topic,8858.msg64297.html#msg64297

and Kloeber's PDF and wiki link:  https://c34.org/bbs/index.php/topic,8136.0.html